Mobile instruments stand up to storms for science

Tuesday

Jun 26, 2007 at 11:08 AMJun 26, 2007 at 11:26 AM

NIKKI BUSKEY Staff Writer

HOUMA -- While most of us try to move out of the path of an oncoming hurricane, scientists with the U.S. Geological Survey will descend on an area before a storm hits to set up portable gauges and tools in the name of science.

Itís part of a new effort by the federal agency tested during Hurricane Rita, where crews will set up between 50 and 150 temporary gauges capable of accurately measuring the intensity of a storm.

The gauges are strapped to a solid structure and, when placed in the path of an oncoming storm, can help scientists figure out how high a storm surge gets, how long it took to come in, how big the stormís waves get and how long the water takes to recede.

"From a safety standpoint, we like to get them out 72 hours before landfall, but in some cases my guys are out anywhere as close as six hours before landfall," said Charles Demas, director of the U.S. Geological Survey Louisiana Water Science Center.

"We use these strong strappings with locking ratchet mechanisms to attach them to structures we know wonít be moved. That way we can deploy them anywhere," he said

Before Hurricane Katrina, the agency relied on readings from a series of fixed gauges that were placed all over the coast.

"We just had to hope they survived the storm," Demas said.

When Katrina damaged 23 of these fixed gauges, scientists decided there had to be a better way.

In the face of Rita, the group set up 37 of the mobile measurers from Abbeville to Beaumont, Texas.

These gauges measure the change in pressure as waves begin to pass over them. And by subtracting the local barometric pressure, scientists can get an accurate measure of what the water height is, even in high-energy areas where houses were reduced to slabs, Demas said.

Traditional methods of measuring can be as much as 1 to 2 feet off, Demas added.

"We got a really good picture of how the storm came ashore," he said about the new measurements taken from Rita. The data was provided to the National Oceanic and Atmospheric Administration and others to help create more-precise models of what exactly happens with storm-surge energy during a storm.

The scientists also hope to apply the data to wetland research, using hard data to get a picture of just how much coastal marshes really do slow down an oncoming storm.

The idea that marshes slow storm surge has been long repeated by coastal advocates but is not backed by hard data, Demas said.

The instruments record pressure data every 30 seconds, and can operate for as long as four days to give scientists "the whole picture," Demas said.

While the USGS does not do modeling themselves, Demas said the agency was so "excited" about the results of the data, that the mobile storm-gauge technique has been adopted by the entire USGS.

The Louisiana office will be deployed across four states in case of a storm, including Texas and Mississippi and Alabama.

The mobile gauges are about the size of a pipe and cost about a thousand dollars, said Steve Blanchard, chief of the USGS water-sciences center in Virginia. The agency is also undergoing an overhaul of its permanent gauges, which record even more storm data.

Scientists are "hardening" 19 of the 59 gauges in strategic locations by building them higher and stronger. The gauges will be able to withstand a flood so strong it might only occur once every 200 years, Demas said. There will be at least one of these tough gauges located in each of the coastal parishes.